Cranial reference mount

ABSTRACT

A surgical guide assembly includes a body having an opening formed at least partially therethrough. An arm extends from the body. A joint is positioned at least partially in the arm. The joint includes an outer ring and an inner ring. The inner ring is configured to move with respect to the outer ring such that an angle between a central longitudinal axis through the inner ring varies with respect to a central longitudinal axis through the outer ring.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application Ser. Nos. 61/910,204, filed Nov. 29, 2013; 61/940,196, filed Feb. 14, 2014; and 62/049,866, filed Sep. 12, 2014, each of which is hereby incorporated by reference in its entirety.

GOVERNMENT SUPPORT STATEMENT

This invention was made with government support under NCATS Grant No. UL1TR000424-06 awarded by the National Institutes of Health. The government has certain rights in the invention.

FIELD OF THE INVENTION

This invention relates generally to the field of surgery, particularly craniomaxillofacial surgery, and specifically to the field of computer-assisted craniomaxillofacial surgery and all related orthognathic, neurosurgical and head/face/neck surgical procedures and associated methods, tools, and systems.

BACKGROUND OF THE INVENTION

Facial transplantation represents one of the most complicated scenarios in craniomaxillofacial surgery due to skeletal, aesthetic, and dental discrepancies between donor and recipient. Use of computer technology to improve accuracy and precision of craniomaxillofacial surgical procedures has been described for nearly 30 years, since the increasing availability of computed topography (CT) prompted the development of a CT-based surgical simulation plan for osteotomies.

Two broad approaches to computer-assisted surgery (CAS) have gained popularity:

-   1) pre-operative computer surgical planning and the use of     three-dimensional computer manufactured surgical guides (3D CAD/CAM)     to cut and reposition bone and soft tissue, and -   2) utilizing intraoperative feedback relative to preoperative     imaging for the surgeon to provide more objective data on what is     happening beyond the “eyeball test.” However, none are meant for     real-time placement feedback in areas where guide placement is more     challenging, such as the three-dimensional facial skeleton. Also,     there are no single platforms built to provide BOTH planning AND     navigation—with seemless integration. Additionally, standard     off-the-shelf vendor computer-assisted surgery systems may not     provide custom features to mitigate problems associated with the     increased complexity of this particular procedure. Furthermore,     there are currently no validated methods for optimizing outcomes     related to facial (e.g., soft tissue), skeletal (e.g., hard tissue),     and occlusal (e.g., dental) inconsistencies in the setting of     donor-to-recipient anthropometric mismatch—a major hurdle to     achieving this specialty's full potential.

One known system includes pre-operative planning and cutting guides by way of computer manufactured stereolithographic models for human facial transplantation. However, such a system uses standard off-the-shelf vendor systems and does not include necessary features to mitigate the increased complexity of this particular procedure.

Additionally, known CAS paradigms for craniomaxillofacial surgery provide little capacity for intraoperative plan updates. This feature becomes especially important since, in some circumstances during the transplantation surgery, it may be necessary to revise and update the preoperative plans intraoperatively.

What is needed in the art, therefore, is a single, fully-integrated platform, providing a computer-assisted surgery solution customized for pre-operative planning, intraoperative navigation, and dynamic, instantaneous feedback—in the form of biomechanical simulation and real-time cephalometrics—for facial transplantation that addresses common shortcomings of existing CAS systems and has the potential to improve outcomes across both the pediatric and adult-based patient population.

SUMMARY

A surgical guide assembly is disclosed. The guide assembly includes a body having an opening formed at least partially therethrough. An arm extends from the body. A joint is positioned at least partially in the arm. The joint includes an outer ring and an inner ring. The inner ring is configured to move with respect to the outer ring such that an angle between a central longitudinal axis through the inner ring varies with respect to a central longitudinal axis through the outer ring.

In another embodiment, the surgical guide assembly includes a body having an opening formed at least partially therethrough. A rod is at least partially positioned in the opening in the body. A trackable feature is coupled to the rod. An arm extends from the body. A joint is positioned at least partially in the arm. The joint includes an outer ring and an inner ring. The inner ring is configured to move with respect to the outer ring such that an angle between a central longitudinal axis through the inner ring varies with respect to a central longitudinal axis through the outer ring. The central longitudinal axis through the outer ring is oriented at an angle from about 1 degree to about 85 degrees with respect to a central longitudinal axis through the opening in the body. A sleeve is positioned at least partially in the inner ring. The sleeve is configured to move with respect to the outer ring. An opening is formed through the sleeve.

A method for attaching a surgical guide assembly to a bone is also disclosed. The method includes placing the surgical guide assembly against the bone or soft tissue covering the bone. The surgical guide assembly includes a body having an opening formed at least partially therethrough. An arm extends from the body. A joint is positioned at least partially in the arm. The joint includes an outer ring and an inner ring. The inner ring is configured to move with respect to the outer ring such that an angle between a central longitudinal axis through the inner ring varies with respect to a central longitudinal axis through the outer ring. A screw is inserted into an opening in the inner ring and at least partially into the bone. The screw couples the surgical guide assembly to the bone.

Additional advantages of the embodiments will be set forth in part in the description which follows, and in part will be understood from the description, or may be learned by practice of the invention. The advantages will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a surgical system and method that closes the loop between surgical planning, navigation, and enabling intraoperative updates to a surgical plan.

FIGS. 2A-2C provide a schematic overview of a surgical system.

FIGS. 2D-2G are graphical representations of some components and/or features of the surgical system of FIGS. 2A-2C.

FIG. 3 is a flow chart depicting a procedure associated with use of the surgical system, for example, the surgical system of FIGS. 2A-2C.

FIG. 4A is a CT-scan of reconstructed images of a size-mismatched facial skeleton generated from segmentation software utilized for pre-operative planning.

FIG. 4B shows a segmented arterial system of a craniomaxillofacial skeleton generated from CT angiography (CTA) data allowing 3D, intraoperative mapping.

FIGS. 5A-5B show depictions of on-screen images provided by a surgical system, such as the surgical system of FIG. 2A displaying real-time, dynamic cephalometrics and pertinent measurements applicable to humans. FIG. 5A shows a donor's face-jaw-teeth alloflap in suboptimal position as compared to a recipient's cranium. FIG. 5B shows appropriate face-jaw-teeth positioning with immediate surgeon feedback and updated cephalometric data pertinent to a pre-clinical investigation. A surgeon may adjust the position of face-jaw-teeth segment upwards, downwards, forwards, or backwards based on this real-time cephalometric feedback, as this information helps to predict optimal form and function. For instance, placing the face-jaw-teeth segment forward may improve the patient's airway, but if moved too far forward, it may cause the patient to have a significant overjet (i.e. malocclusion) and abnormal appearance in a profile view.

FIG. 6 shows some pre-bent fixation plates with screw holes designed virtually to accommodate the donor-to-recipient skeletal mismatch areas and matching navigational cutting guides of a surgical system, for example, the surgical system of FIGS. 2A-2C.

FIG. 7A is a photograph of a kinematic reference mount of an embodiment as it is affixed onto a donor's cranium with intermaxillary screws. A permanent suture (not visible) attaches stabilizers, such as springs and/or cross bars, which allow easy removal and replacement during surgery.

FIG. 7B is a photograph of a detachable rigid body with reflective markers attached to the reference body

FIGS. 8A-8C are illustrations of cutting guides of the embodiments with navigational capabilities. FIG. 8A illustrates a donor face-jaw-teeth alloflap recovery, FIG. 8B shows a recipient preparation prior to transplant, and FIG. 8C illustrates a custom pre-bent fixation plate and palatal splint designed to achieve face-jaw-teeth alignment and skeletal inset.

FIGS. 9A-9D are photographs and renderings showing exemplary surgical results.

FIGS. 10A-10C are a top-view (bird's eye view), a left-sided profile view, and a frontal view, respectively, of images displayed by an imaging system of a surgical system. The images depict a recipient skeleton and include real-time assessment of planned versus actual face-jaw-teeth positions.

FIGS. 11A-11B are “on screen” images displayed by an imaging sub-system of a surgical system. The images depict an ideal location of a cutting guide versus an actual position and an actual inset position of a donor alloflap for aesthetic, dental, and skeletal relation in size-mismatched donors due to anterior translation of cutting guide.

FIG. 12 illustrates a virtual osteotomy and planned cut plane placement on virtual representations of a skeletal feature.

FIG. 13 shows a virtual placement of a cutting guide alongside photographs of an actual placement.

FIG. 14A illustrates a perspective view of a variation of a cutting guide, for example, a variation of the cutting guide of FIG. 13.

FIG. 14B illustrates a top view of a variation of a cutting guide, for example, a variation of the cutting guide of FIG. 13.

FIG. 15 illustrates a perspective view of a surgical guide assembly.

FIG. 16 illustrates a side, cross-sectional view of the surgical guide assembly shown in FIG. 15.

FIG. 17 illustrates an exploded side, cross-sectional view of the surgical guide assembly shown in FIG. 15.

FIG. 18 illustrates a perspective view of the surgical guide assembly shown in FIG. 15 with thumbscrews for securing a position of swivel joints.

FIG. 19 illustrates a side, cross-sectional view of the surgical guide assembly shown in FIG. 18.

FIG. 20 illustrates an exploded side, cross-sectional view of the surgical guide assembly shown in FIG. 18.

FIG. 21 illustrates a perspective view of the surgical guide assembly coupled to a skull.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present embodiments, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5. In certain cases, the numerical values as stated for the parameter can take on negative values. In this case, the example value of range stated as “less that 10” can assume negative values, e.g. −1, −2, −3, −10, −20, −30, etc.

The following embodiments are described for illustrative purposes only with reference to the Figures. Those of skill in the art will appreciate that the following description is exemplary in nature, and that various modifications to the parameters set forth herein could be made without departing from the scope of the present invention. It is intended that the specification and examples be considered as examples only. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

Disclosed are embodiments of a computer-assisted surgery system that provides for large animal and human pre-operative planning, intraoperative navigation which includes trackable surgical cutting guides, and dynamic, real-time instantaneous feedback of cephalometric measurements/angles as needed for medical procedures, such as facial transplantation, and many other instances of craniomaxillofacial and orthognathic surgery. Such a system can be referred to as a computer-assisted planning and execution (C.A.P.E.) system and can be exploited in complex craniomaxillofacial surgery like Le Fort-based, face-jaw-teeth transplantation, for example, and any type of orthognathic surgical procedure affecting one's dental alignment, and can include cross-gender facial transplantation.

The fundamental paradigm for computer-assisted surgery (CAS) involves developing a surgical plan, registering the plan and instruments with respect to the patient, and carrying out the procedure according to the plan. Embodiments described herein include features for workstation modules within a CAS paradigm. As shown in FIG. 1, a surgical system of the embodiments can enable intraoperative evaluation of a surgical plan and can provide instrumentation for intraoperative plan updates/revisions when needed.

Embodiments can include a system with integrated planning and navigation modules, for example, a system for tracking donor and recipient surgical procedures simultaneously. In general, features of such a system can include: 1) two or more networked workstations concurrently used in planning and navigation of the two simultaneous surgeries for both donor and recipient irrespective of geographic proximity, 2) two or more trackers, such as electromagnetic trackers, optical trackers (e.g., Polaris, NDI Inc.), and the like, for tracking bone fragments, tools, and soft tissues, 3) one or more guides, reference kinematic markers, etc. as required for navigation. These features are described in further detail with respect to FIGS. 2A-2G.

Preoperative planning can include the following tasks: a) segmentation and volumetric reconstruction of the donor and recipient facial anatomy; b) planning for patient-specific cutting guide placement; c) cephalometric analysis and biomedical simulation of the hybrid skeleton's occlusion and masticatory function, respectively; d) fabrication of the hybrid cutting guides enabling both geometric (“snap-on” fit) and optical navigation; e) 3D mapping the vascular system on both recipient and donor facial anatomy; and f) plan updates, if necessary, based on the feedback from the intraoperative module. As used herein, “snap-on fit” or “snap-on” or “snap on” is used to describe the way an item, such as a cutting guide, attaches to a pre-determined area. That is, the cutting guide actually “snaps-on” to a certain pre-determined area along the facial skeleton, and in all other areas it doesn't fit properly since size and width varies throughout significantly with many convexities and concavities.

Intraoperative tasks of embodiments described herein can generally include: 1) registering the preoperative model reconstructed from the CT data to donor and recipient anatomy; 2) visualizing (e.g., using information from the tracker, such as an electromagnetic tracker, optical tracker, and the like) the instruments and cutting guides to help the surgeon navigate; 3) verifying the placement of cutting guides, and performing real-time cephalometric and biomechanical simulation for occlusion analysis, if, for any reason, the osteotomy sites need to be revised; 4) dynamically tracking the attachment of the donor fragment to the recipient and providing quantitative and qualitative (e.g., visual) feedback to the surgeon for the purpose of improving final outcomes related to form (i.e., overall facial aesthetics) and function (i.e., mastication, occlusion relation, airway patency). Such a procedure is described in further detail below with respect to FIG. 3.

Preoperative Planning

In general, a method for performing a surgery includes a virtual surgical planning step that includes performing segmentation and 3D reconstruction of recipient and donor CT scans (e.g., Mimics 15.01, Materialise, Leuven Belgium). Virtual osteotomies can then be performed within the software to optimize the donor/recipient match. Patient-customized cutting guide templates can then be created (3-matic 7.01, Materialize, Leuven, Belgium). These templates can then be rapid-prototyped via an additive manufacturing modeling process, which can include, but is not limited to, stereolithography or 3D printing and the like. The surgical method and system for performing surgery are described in further detail below.

Referring to FIGS. 4A and 4B, during the initial planning stage, surgeons determine a virtual plan 401 based on the recipient's craniomaxillofacial deformity irrespective of the donor. From registered CT data, segmentation software generates volume data for specific key elements (e.g., the mandible, maxilla, and cranium) used for preoperative planning and visualization. The planning workstation automatically generates the expected cut geometry of the donor fragment 402 together with the recipient, thereby defining the predicted facial skeleton with accompanying hybrid occlusion. If available, blood vessels 404 are segmented from CT angiography scans as shown in FIG. 4B. That is, in an embodiment, nerves (via known nerve foramens) and vessels (both arteries and veins) can be localized to provide a full anatomical “road map” to the surgeons for a more precise, time-saving anatomical dissection with perhaps decreased blood loss and smaller incisions. The planning module can also perform static cephalometric analysis and evaluation of face-jaw-teeth harmony via biomechanical simulation on varying constructions of the hybrid donor and recipient jaw, such as that shown in FIGS. 5A-5B. Using this tool, the surgeon can evaluate different placements for the donor's face-jaw-teeth alloflap on the recipient's facial skeleton in relation to orbital volumes, airway patency, facial projection, and dental alignment. An automated cephalometric computation for the hybrid face indicates the validity of the planned surgery from both an aesthetic, functional, and reconstructive standpoint based on various measurements of pertinent landmarks as shown, for example, in Tables 1A-B.

TABLE 1A Pertinent landmarks for cephalometric analysis SYMBOL NAME and DEFINITION Go Gonion: a point mid-way between points defining angles of the mandible Gn Gnathion: most convex point located at the symphysis of the mandible ALV Alveolare: mid-line of alveolar process of the upper jaw, at incisor - alveolar junction LIB Lower Incisor Base: midline of anterior border of alveolar process of mandible at the incisor-alveolar junction PA Parietale: most superior aspect of skull in the midline, (formed by nuchal crest of occipital bone and parietal bone) PRN Pronasale: bony landmark representing anterior limit of nasal bone ZY Zygion: most lateral point of malar bone OCC Occipital region: midpoint between the occipital condyles

TABLE 1B Cephalometric measurements and related units. Measure LIB- PA- PA- ALV- ZY- PA- Go- Go- PA- LIB- OCC- PA- PRN- PRN- PRN- ZY PRN Gn LIB ALV ALV Overbite Overjet PRN ALV ALV LIB LIB Units mm mm mm Mm mm mm mm mm mm deg deg deg deg

To evaluate and predict cephalometric relationships both during planning and intra-operative environments, the system can use validated, translational landmarks between swine and human to thereby allow effective pre-clinical investigation. The cephalometric parameters defined by these landmarks can be automatically recalculated as the surgeon relocates the bone fragments using a workstation's graphical user interface.

Preoperative planning can also involve fabrication of custom guides 207 (as shown in FIG. 6) and palatal splints 223 (as shown in FIG. 8C). Planned cut planes 403 (as shown in FIG. 4) can be used for defining the geometry of the cutting guides to thereby provide patient-specific cutting guides. These cutting guides can be designed according to the skeletal features through which the cutting plane intersects, such as an outer skeletal surface of a cross section defined by the cutting plane, and can be fabricated via stereolithography, or via any additive manufacture technology. In an embodiment, custom cutting guide templates can be separately designed and navigational registration elements can be added (Freeform Plus, 3D Systems, Rock Hill, S.C.). As discussed above, the surgical guides can be manufactured via additive manufacturing technology (AMT). The cutting guides can, therefore, be a 3D printing material such as a polymer, and can include an attachment surface 216 configured for attaching to a skeletal feature, and can have a “snap-on” fit to both donor and recipient. As described above, the attachment surface may include a contoured surface that corresponds to the contours of the skeletal feature within the planned cut planes. A navigation surface, such as a reference geometry 217 connected, built into, or attached to the guide structure directly or via attachment guides (not shown), enables dynamic intraoperative tracking of guides with respect to the patient's skeleton. Palatal splints ensure planned dento-skeletal alignment fixation following Le Fort-type facial transplants or any similar type of surgery. Fixation plates 216 can include a primary surface 216′ and a plurality of fixation surfaces 221, such as eyelets, for screw placement to provide rigid immobilization at the irregular skeletal contour areas along various donor-to-recipient interfaces. Having pre-bent fixation plates decreases total operative times and helps to confirm accurate skeletal alignment by overcoming step-off deformities at bone-to-bone interfaces. Accordingly, at least one of the plurality of fixation surfaces can be located on one side of the primary surface and configured for attaching the fixation surface to a donor skeleton fragment, and at least one of another of the plurality of fixation surfaces is located on another side of the primary surface and configured for attaching the fixation surface to a recipient skeleton. The whole fixation plate or just portions of the fixation plate, such as the primary surface or fixation surfaces can be manufactured via additive manufacturing technology.

The cutting guide's navigation surface can include trackable objects, for example, on the reference geometry, such as infrared (IR) reflective coatings or IR emitters. For example, the trackable objects can include a plurality of integrated tracking spheres, each of which has an IR reflection surfaces.

Intraoperative Surgical Assistance

Individual navigation for both donor and recipient surgeries tracks the cutting guides with respect to planned positions. Surgeons can attach a reference unit, such as a kinematic reference mount to three intramedullary fixation (IMF) screws arranged in a triangular pattern on each the donor and recipient craniums as shown in FIG. 7A-7B. Accordingly, in an embodiment, there is a reference unit 205 for providing real-time surgical navigation assistance. The reference unit for providing real-time surgical navigation assistance can include a kinematic mount 203, at least one fixation rod 202, at least one support 204, and reference geometry 201. The kinematic mount 203 can include a base with a plurality of recesses defined by sidewalls 233, at least one pair of slots 235 defined by portions of the sidewalls, with each slot of the pair formed across the recess from the other slot, and at least one guide hole 237 extending through a length of the fixation plate. The at least one fixation rod 202 can extend through the at least one guide hole 237. An end of the at least one support rod can be configured for attaching to a skeleton of a being 209. The at least one support can be disposed in the pair of slots and can be configured to attach to the being. The reference geometry 201 can be attached to the at least one fixation rod.

The at least one support 204 can include at least one cross-bar 204′ with ends that are configured for placement in the slots 235, and a spring 204″ attached at one end to the at least one cross-bar 204′ and attached at another end to the patient (e.g., a human-being). The spring attached at another end to the being can be attached via a suture (further described below). The reference unit 205 can further include a trackable object disposed on the reference geometry. The trackable object disposed on the reference geometry can include an IR reflective surface. The mount 203 can be made via additive manufacturing techniques and can therefore include a polymer. The at least one fixation rod can include a plurality of intramedullary fixation screws. The base can be configured for being detachably mounted on the skeleton of the being 209. The intramedullary fixation screws can be arranged in a triangular pattern. Accordingly the guide-holes can be configured in a triangular pattern on the base.

Accordingly, the mount design permits flexibility in the placement of the IMF screws so that no template is necessary. A spring 204″ can attach to each IMF screw via suture threaded through, for example, the eyelets. These springs hold the cranial mount 203 in place and allow easy removal and replacement of the cranial mount (e.g. during positional changes required for bone cuts and soft tissue dissections). This may provide detachability and use of Intramaxillary fixation (IMF) screws for stable attachment.

The reference geometry 201 (e.g., which can be purchased from Brainlab, Westchester, Ill., USA) attached to the kinematic mount 203 provides a static coordinate frame attached to the patient. The surgeon can digitize three bony landmarks (e.g., the inferior aspect of the orbits and antero-superior maxilla) to define a rough registration between the environment and virtual models. For example, three, consistent points can be selected which can be quick to find, easy to reproduce on numerous occasions, and would remain constant irrespective of the user and his/her experience with the systems of the embodiments. The surgeon can thereby collect several point sets from exposed bone using a digitization tool and uses an iterative closest point registration technique to refine the registration. As shown in FIG. 8, once registered, the surgeon navigates the placement of the cutting guide 217 using the combination of “snap-on” geometric design and the tracking system coupled to visual feedback. This allows assessment of inaccuracies related to soft tissue interference, iatrogenic malpositioning, anatomical changes since acquiring original CT scan data, and/or imperfections in cutting guide design or additive manufacturing process.

Self-drilling screws affix the cutting guide to the patient's skeleton to ensure osteotomies are performed along pre-defined planes, maximizing bony congruity. After dissecting the donor's maxillofacial fragment and preparing the recipient's anatomy, the surgical team transfers the facial alloflap. The system is configured to track the final three-dimensional placement of, for example, the Le Fort-based alloflap providing real-time visualization such as that shown in FIG. 5A-5B. This provides real-time visualization of important structures such as new orbital volumes (vertical limit of inset), airway patency (posterior horizontal limit of inset), and facial projection (anterior horizontal limit of inset). Once confirmed, the surgeon fixates the donor alloflap to the recipient following conventional techniques with plates and screws.

Accordingly, returning to FIGS. 2A-2G, there is a system 2000 for tracking donor and recipient surgical procedures simultaneously. The system can include a donor sub-system 200-D, a recipient sub-system 200-R and a communications link (indicated by the horizontal dotted-line) such as a communication link that provides TCP/IP data transfer between the donor and recipient sub-systems. The donor sub-system can include a first computer workstation 215-D, a first cranial reference module 205-D, a first cutting guide 207-D for attaching to a preselected location of a donor skeleton 206, a first fragment reference module 201-D′, and a first tracker 213-D. The first cutting guide 207-D can include an attachment surface 219-R configured for attaching to a skeletal feature, and a navigation surface 217-D connected to the attachment surface and comprising a trackable reference geometry. The first tracker 213-D may be configured to be in communication with the first computer workstation, for example, via a communications link. The first tracker can be configured to track, for example via IR optical tracking, a location of a portion of the first cranial reference module, a portion of the first cutting guide and a portion of the first fragment reference module. The recipient sub-system 200-R can include a second computer workstation 215-R, a second cranial reference module 205-R, and a second tracker 213-R. The second tracker 213-R can be configured to be in communication with the second computer workstation, for example, via a communications link. The second tracker can be configured to track, for example, via IR optical tracking, a location of a portion of the second cranial reference module. The communications link can connect the first computer workstation and the second computer workstation such that the first computer workstation and second computer workstation are able to communicate.

The recipient sub-system 200-R can further include a second fragment reference module 201-R. The second tracker 213-R can further be configured to track a location of a portion of the second fragment unit.

The recipient sub-system 200-R can further include a second cutting guide 219-R for attaching to a preselected location of a recipient skeleton 208. The second tracker 213-R can further be configured to track a location of a portion of the second cutting guide.

Additionally, when a surgeon has removed the donor skeletal fragment from the donor, it can then be transferred for attachment onto the recipient. Accordingly, the second tracker 213-R can be further configured to track a location of a portion of the first cutting guide 207-D so that it can be matched relative a position of the second cranial reference module 205-R.

The first cranial reference unit, the second cranial reference unit, or both the first and second cranial reference units can include a kinematic mount 205 as described above.

Using the system of FIGS. 2A-2G, it is possible to execute a surgical method, such as the surgical method described in FIG. 3. For example, in step 302 a donor, recipient and transplant type are identified. CT/CTA scans of both the donor and recipient are collected and 3D models are created in step 304. The donor and recipients are prepared for surgery with the creation of skin incisions in step 306. The method continues at 307 with attachment of reference guides and performing registration. For example, a first cranial reference unit can be attached to a donor skeleton, a first fragment reference unit can also be attached to the donor skeleton at a location that is different that of the first cranial reference unit. The locations of the first cranial reference unit and the first fragment reference unit can be tracked with a first tracker. 3D reconstructions of the donor skeleton can be constructed showing a first virtual cranial reference unit and first virtual fragment reference unit superimposed on the first 3D reconstruction at locations that correspond to relative positions of the first cranial reference unit and the first fragment reference unit.

A second cranial reference unit can be attached to a recipient skeleton. A second location of the second cranial reference unit can be tracked with a second tracker. A second 3D reconstruction of the recipient skeleton can be created with a second virtual cranial reference unit superimposed on the second 3D reconstruction at a location that corresponds to a location of the second cranial reference unit. At 308, vessels and nerves are dissected and exposed. At this stage, navigation of the patient-specific cutting guides can occur, with plan revision and updates provided periodically. For example, a first cutting guide, such as a patient-specific cutting guide according to the descriptions provided above, can be attached onto the donor skeleton at a preselected location such as that corresponding to a planned cut-plane. The location of the first cutting guide can be tracked with the first tracker. A first virtual cutting guide can be superimposed on the first 3D reconstruction at a location that corresponds to a location of the first cutting guide relative to the location of the first cranial reference unit or the location of the first fragment reference unit.

A first virtual fragment can be formed by segmenting the 3D reconstruction of the donor skeleton at a location adjacent to the first virtual cutting guide. The first virtual fragment can be superimposed on the second 3D reconstruction of the recipient skeleton.

At step 310, a surgeon can perform an osteotomy on the donor skeleton to remove the first fragment but cutting the skeleton along a cutting path defined by the first cutting guide. Upon transferring the removed skeletal fragment from the donor, the first cutting guide can be tracked, by the second tracker, for example, when the fragment is brought near the recipient for attachment. The surgeon can then navigate placement of the cutting guide as it is dynamically tracked at step 311, and will receive feedback from the system such as by referring to a first virtual fragment that is superimposed on the second 3D reconstruction to form a hybrid 3D reconstruction. At step 312, the first fragment can then be attached to the recipient skeleton via known surgical methods and the incisions can be sutured in step 314.

The step of superimposing the first virtual fragment on the second 3D reconstruction of the recipient skeleton can include performing an automated cephalometric computation for the hybrid reconstruction. In fact, the step of superimposing the first virtual fragment on the second 3D reconstruction can include providing a communications link between a first workstation on which the first 3D reconstruction is displayed and a second workstation on which the second 3D reconstruction is displayed, and initiating a data transfer protocol that causes the first workstation and the second workstation to send electronic signals through the communications link.

Surgical methods of the embodiments described above can also include attaching a second cutting guide at a preselected location on the recipient skeleton. The second cutting guide can also include features of the cutting guide described above.

For the surgical methods of embodiments described herein the donor skeleton can include a male skeleton or a female skeleton and the recipient skeleton can include a female skeleton. Alternatively, the donor skeleton can include a male or female skeleton and the recipient skeleton can include a male skeleton.

Surgical methods of the embodiments can further include steps for assessing a size-mismatch between the donor skeleton and the recipient skeleton by measuring a dorsal maxillary interface between the first fragment and recipient skeleton. In an embodiment, the surgical method can include selecting a location of the first fragment onto the recipient skeleton that minimizes dorsal step-off deformity at the area of osteosynthesis. In an embodiment, the first cutting guide, the second cutting guide, or both the first cutting guide and the second guide may be or include concentric cutting guides.

Surgical methods of embodiments can further include mapping the vascular system on the facial anatomy of both the recipient and the donor and superimposing corresponding virtual representations of the vascular system and the facial anatomy onto the first 3D representation, such as shown in FIG. 4B

Surgical methods of embodiments can include a method for registration of a preoperative model, for example a model reconstructed from CT data, to donor and recipient anatomy. Such a method can include: creating a plurality of indentations on the donor skeleton, creating a plurality of virtual markers on the first 3D reconstruction of the donor skeleton corresponding to the locations of the indentations on the donor skeleton, placing a trackable object on at least one of the plurality of indentations, and determining whether a subsequent location of the virtual markers is within a predetermined tolerance relative to an actual subsequent location of the indentations.

EXAMPLES Example 1

Live transplant surgeries (n=2) between four size-mismatched swine investigated whether or not an embodiment could actually assist a surgical team in planning and executing a desired surgical plan. As shown in FIGS. 9A-9B, the first live surgery confirmed the proposed utility of overcoming soft and hard tissue discrepancies related to function and aesthetics. The final occlusal plane within the first recipient was ideal and consistent with the virtual plan as seen on lateral cephalogram as shown in FIG. 10C. Pre-operative functional predictions of donor-to-recipient occlusion were realized based on cephalometric analyses as shown in FIG. 9C performed both before and after surgery. Soft tissue inconsistencies of the larger-to-smaller swine scenario were also reduced following the predicted movements of face, jaw and teeth as shown in FIG. 10D.

The second live surgery showed improved success as compared to its predecessor due to surgeon familiarity and technology modifications. System improvements and growing comfort of the surgeons led to reduced operative times for both donor and recipient surgeries. Overall the surgical time reduced from over 14 hours to less than 8 hours due to improved surgical workflow and increased comfort with a system of an embodiment.

Based on the results obtained in the live and plastic bone surgeries, the functions associated with setting up a system of an embodiment (attaching references, performing registration, attaching cutting guides) adds about 11 minutes to the total length of surgery.

The system also recorded information, such as rendering information which can be stored in a storage medium of a workstation, relating the donor fragment 1002 to the recipient 1010 qualitatively as shown by color mismatch 1004, which matched the post-operative CT data as shown in FIG. 10. The recipient cutting guide 1107′ was not placed as planned 1107 due to an unexpected collision between the cranial reference mount and the recipient cutting guide as shown in FIGS. 11A-11B. In this case, there was anterior translation of the cutting guide (toward the tip of the swine's snout) by approximately 4 cm.

Overall, the donor 1106 and recipient craniums (n=4) 1108 were registered successfully to the reference bodies for both live surgeries. The model to patient registration error across the surgeries was 0.6 (+/−0.24) mm. The cutting guide designs of the embodiments proved highly useful in carrying out the planned bone cuts, which compensated for size-mismatch discrepancies between donor and recipient. Marking spheres fixated to the guides allowed real-time movement tracking and “on-table” alloflap superimposition onto the recipient thereby allowing visualization of the final transplant result.

Example 2

Female and male donor heads (n=2), double-jaw, Le Fort III-based alloflaps were harvested using handheld osteotomes, a reciprocating saw, and a fine vibrating reciprocating saw. Both osteocutaneous alloflaps were harvested using a double-jaw, Le Fort III-based design (a craniomaxillofacial disjunction), with preservation of the pterygoid plates, incorporating all of the midfacial skeleton, complete anterior mandible with dentition, and overlying soft tissue components necessary for ideal reconstruction.

Prior to transplantation, both scenarios were completed virtually given the gender-specific challenges to allow custom guide fabrication as shown in panels A-H of FIG. 12. Once assimilated, the donor orthognathic two-jaw units were placed into external maxilla-mandibular fixation (MMF) using screw-fixated cutting guides to retain occlusal relationships during the mock transplants as shown in panels A-D of FIG. 13.

As shown in FIGS. 13, 14A-14B, an embodiment of a cutting guide 1307 can include a frame 1307′ with at least one attachment surface 1319, for example 1 to 6 attachment surfaces, configured for attaching the cutting guide to a skeletal feature. The cutting guide can include a navigation surface 1317 (not shown in FIG. 13) connected to the frame. The navigation surface can include a reference geometry that can be tracked by a tracker, for example, via IR optical tracking. The at least one attachment surface 1319 can include a contoured surface corresponding to contours of portions of the skeletal feature, for example, such as the contours of a skeletal feature that intersect a planned-cut plane as indicated by 1319′ in FIG. 12. The at least one attachment surface 1319 can be detachably connected to a skeletal feature. The at least one attachment surface 1319 can be detachably connected to an attachment guide 1341. The attachment guide 1341 can be detachably connected to a portion of the frame 1307′. For example, attachment guides 1341 can be detachably connected via slots integrated into frame 1307′, or held in place against frame 1307 with screws or the like. In another embodiment, attachment guides 1341 are formed as portions of frame 1307′ but can be removed. The frame can have a ring-like shape (as shown in FIG. 13) or can have a cylinder-like shape (as shown in FIG. 14A). Frame 1307′ having a cylinder like shape can have a bottom surface 1307″ that rests against a patient's soft tissue to provide support for the frame.

For example, during a surgical procedure, 3D reconstructions of portions of a donor skeleton are created. Planned cutting planes are selected and a cutting guide with attachment surfaces having a contoured surface corresponding to contours of portions of the skeletal feature, for example, such as the contours of a skeletal feature that intersect a planned-cut plane, is designed. The designed cutting guide is manufactured via, for example, an additive manufacturing process. The designed cutting guide with an integrated navigation surface is attached to the patient. For example, the cutting guide can be designed such that it has a snap-on fit over the skeletal feature, which can be further secured to the skeletal feature with set screws. A surgeon removes a donor skeletal fragment with the cutting guide attached to the fragment. The donor skeletal fragment is then attached to the recipient. As the donor skeletal fragment is attached to the recipient, the attachment surfaces are removed from the donor fragment. For example, each of the attachment guides 1341 with a corresponding attachment surface 1319 can be detached from the frame 1307′. As this occurs, a cylindrical shaped frame 1307′ has a bottom surface 1307″ that rests against the soft tissue of the patient to provide stability for the remaining portions of the cutting guide and to hold the navigation surface 1317′ in place.

While the disclosure has been illustrated respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. For example, the embodiments described herein can be used for navigation and modeling for osteotomy guidance during double-jaw face transplantation, single-jaw maxillofacial transplantation, and any other neurosurgical, ENT/head and neck surgery, or oral maxillofacial surgical procedure alike.

Embodiments described herein can include platforms for preoperative planning and intraoperative predictions related to soft tissue-skeletal-dental alignment with real-time tracking of cutting guides for two mismatched jaws of varying width, height and projection. Additional safeguards, such as collection of confidence points, further enable intraoperative verification of the system accuracy. This, in addition to performing real-time plan verification via tracking and dynamic cephalometry, can considerably increase the robustness of the systems described herein. Moreover, systems of embodiments can include a modular system that allows additional functionality to be continually added.

Embodiments described herein can include an approach for resolving conflicts in case of position discrepancies between the placement of the guide and the guide position prompted by the navigation software. Such discrepancy may be due to either the guide (soft tissue interference, iatrogenic malpositioning, changes since the CT data was obtained or imperfections in cutting guide construction/printing), and/or the navigation system (e.g. registration error, or unintended movement of the kinematic markers). To resolve these source(s) of discrepancy, four indentations can be created on a bone fragment (confidence points) where a reference kinematic marker is attached. At any time during an operation, a surgeon can use a digitizer and compare the consistency of the reported coordinates of the indentations via navigation to their coordinates with respect to a virtual computer model.

Embodiments described herein can include a system that provides real-time dynamic cephalometrics and masticatory muscle biomechanical simulation for both planning and intraoperative guidance to ensure ideal outcomes in craniomaxillofacial surgery.

Additional Embodiments

Osseointegrated Dental Implants

Patients with poor or missing dentitions may require dental implants to improve mastication. A popular modality with increasing indications includes “osseointegrated dental implants”. Oseeointegrated dental implants can include, and may consist of, a two-piece permanent implant device, which is placed into either the maxilla or mandible skeleton with a power drill for placement and stability. A second piece, in the shape of a tooth is screwed onto the secure base. An embodiment of the CAPE system described above can be used to provide the dentist or surgeon real-time cephalomteric feedback in an effort to restore ideal occlusion and predict optimized mastication with biomechanical predictions—as similar to maxillofacial transplantation. As such, the dentist or surgeon placing these items needs to know the bone stock quality of the jaw(s) and angle to place the framework.

Osseointegrated Craniofacial Prosthetics

Patients with severe cranial or facial disfigurement may be poor surgical candidates due to overwhelming co-morbities and/or because of an accompanying poor prognosis. Therefore, to help return these patients into society, some use craniofacial prosthetics as a way to restore “normalcy”. Application of these three-dimensional prosthetics replacing absent craniofacial features (i.e., nose, eye, etc.) may either be hand-molded/painted by an anaplastologist or printed with 3D technology by a prosthetician. Either way, in an embodiment, the CAPE system described above can provide a one-stop solution for patients requiring alloplastic and/or bioengineered prosthetic reconstruction for large craniomaxillofacial deformities. The craniofacial implants can be tracked as similar to a donor face-jaw-teeth segment described above. For example, pre-placement images of the prosthetic may be fabricated, and surgical plans may be optimized since these appliances are placed with osseointegrated devices as similar to dental implants described above—with rigid plates and screws. As such, the surgeon placing them needs to know the bone stock quality and angle to place the framework, and also needs to know with visual feedback as to the ideal position in three-dimensional space.

Craniomaxillofacial Trauma Reconstruction

Patients suffering from acute or chronic facial disfigurement are often seen by a craniomaxillofacial surgeon. Both penetrating and/or blunt trauma may cause significant damage to the underlying facial skeleton. As such, in an embodiment, the CAPE system technology described herein allows the surgeon to assess and optimize bone fragment reduction and reconstruction with real-time feedback. In addition, fractures affecting the jaws can be aided by real-time cephalometrics in hopes to restore the patient back to their pre-trauma angle/measurements (as a way to assure proper occlusion). Navigation, as described above in an embodiment of the CAPE system, can be exceptionally helpful for orbit fractures around the eye or cranial fractures around the brain, since the nerve anatomy is delicate and consistent—which makes it applicable to the CAPE system. In summary, a surgeon (including the likes of a Plastic surgeon, ENT surgeon, oral/OMFS surgeon, oculoplastic surgeon, neurosurgeon) reducing craniofacial fractures needs to know the bone stock quality remaining, where plates/screws are best placed, and the optimal plan prior to entering the operating room.

Neurosurgical Procedures

Neurosurgeons frequently perform delicate craniotomies for access for brain surgery. Currently, there are several navigational systems available. However, none of the conventional systems include features described in the embodiments of the CAPE platform as described above. That is, the conventional systems lack the ability to assist both pre-operatively with planning AND with intra-operative navigation for execution assistance. In addition, the current neurosurgery systems require the head to be placed in antiquated “bilateral skull clamp pins” during the all or a portion of the surgery. This means that before each neurosurgery procedure starts, a big 3-piece clamp is crunched onto the skull of the patient to make sure the head does not move during surgery, particularly to allow for use of the conventional navigation systems. However, embodiments of the CAPE system, such as those described above, use a small, modified rigid cranial reference mount which removes the need for using a big, bulky clamp from the field and allows the surgeon to rotate the patient's head if and when needed. To a craniofacial plastic surgeon, who often is consulted to assist with simultaneous scalp reconstruction, elimination/removal of such pins from the surgical field is a huge advantage. For example, elimination of the pins makes scalp reconstruction in the setting of neurosurgery much safer since the pins aren't present to hold back mobilization and dissection of the nearby scalp, which is needed often for complex closure. It also, reduces the risk of surgical contamination since the current setup with pins is bulky and makes surgical draping and sterility much more difficult and awkward. A small cranial mount as part of the CAPE system is a huge advancement for the field.

Congenital Deformity Correction

Unfortunately, newborns are commonly born with craniofacial deformities to either maternal exposure or genetic abnormalities. As such, they may have major development problems with their skeleton and the overlying structures (eyes, ears, nose) may therefore appear abnormal. In addition, newborns may suffer from craniosynostosis (premature fusing of their cranial sutures) which causes major shifts in the shape of their head at birth. In an embodiment, the CAPE system described above, can be utilized to address such congenital deformities, irrespective of etiology. For example, if a 16 year old needs to have major Le Fort surgery to move the central facial skeleton into better position forward to improve breathing, mastication, and appearance, use of the CAPE system technology for both pre- and intra-operatively provides a huge advancement for the field.

Head/Neck and Facial Reconstruction (ENT Surgery)

Head and neck surgeons in the specialty of Otolarygology (ENT) are frequently reconstructing facial skeletons. Reasons include post-tumor resection, facial trauma, aesthetic improvement, congenital causes and/or functional improvement (nose, mouth, eyes, etc.). Therefore, this specialty would greatly benefit from use of the CAPE system technology described herein. For example, in an embodiment, use of the CAPE system can be used in a wide range of surgeries including such instances as post-trauma fracture reduction/fixation, free tissue transfer planning and execution (i.e., free flap reconstruction with microsurgical fibula flaps for large bone defects where the leg bone receives dental implants for jaw reconstruction), smaller jaw reconstruction cases with implant materials, and/or anterior skull base reconstructions with neurosurgery following tumor resection. This specialty is very diverse, and therefore the CAPE system's easy adaptability can help make it greatly valuable to this group of surgeons.

Orthognathic Surgery

Orthognathic surgery describes any of surgical procedure type moving the jaw and/or jaw-teeth segments. This is most commonly performed by either oral surgeons, oral-maxillofacial surgeons (OMFS), or plastic surgeons. It is done currently both in the hospital as an insurance case or in the outpatient setting for a fee-for-service. It may be indicated for enhanced mastication, improved aesthetics, and/or both reasons. Having the ability to plan and predict jaw movements based on biomechanical muscle (i.e., external) forces will be immensely valuable to this field. In an embodiment, surgeons can utilize the CAPE system described above to predict functional jaw movements both at time of surgery and after surgery (1, 5, 10, 20 years post-op). In addition, in an embodiment, a surgeon can utilize the CAPE system to provide real-time cephalometric feedback, which provides an advancement not seen in the conventional systems. In comparison, for the last several centuries, oral surgeons have used splints fabricated in the dental lab pre-operatively for assistance in the operating room to help confirm dental alignment as planned. This takes time (e.g., 4-6 hours to make by hand), effort, and money. In contrast to the conventional systems, surgeons utilizing the CAPE system can go to the operating room with pre-fabricated cutting guides and tracking instruments, cut the jaws where planned, and then match the teeth on the table based on real-time cepholmetric feedback and biomechanical jaw simulation to predict post-operative mastication—unlike ever before. For example, use of the CAPE system will allow surgeons to know instantaneously if the aesthetic and functional angles/measurements are ideal and where they should be. In addition, the CAPE system is able to supply palatal cutting guides and pre-bent metal fixation plates (as opposed to the conventional methods that require handbending each plate for proper shape). In summary, the CAPE system will be a “game-changer” for orthognathic surgery.

“Computer-Assisted Cranioplasty”

This application aims at improving immediate surgical repair of large crani al defects (>5 cm²) with customized craniofacial inmplants following benign/malignant skull neoplasm (tumor) resection (i.e., referred to as “single-stage implant cranioplasty”). Currently, it is challenging to reconstruct these patients with pre-fabricated implants since the actual size/shape is unknown until the tumor is removed. We therefore envision using our novel computer-assisted surgical workstation to significantly reduce the intraoperative time used for reshaping/resizing the customized implant. The workstation will provide visualization related to the tumor, the resulting skull defect, and the reshaped implant for exact positioning. This development will build upon this Computer-Assisted Planning and Execution (CAPE) system for Le Fort-based, Face-Jaw-Teeth transplantation and will help to improve both the pre-operative planning and intra-operative execution of single-stage implant cranioplasties. Cranioplasties are performed to reconstruct large defects following stroke, trauma, aneurysmal bleeding, bone flap removal for infection, and oncological ablation. However, oncological defects are commonly reconstructed with “off-the-shelf” materials, as opposed to using a pre-fabricated customized implant—simply because the exact defect size/shape is unknown. With this in mind, this disclosure provides the surgeon with a computer-assisted algorithm to allow him/her to reconstruct tumor defects with pre-customized cranial implants (CCIs) for an ideal result.

Nearly 250,000 primary brain tumors/skull-based neoplasms are diagnosed each year resulting in a range of 4500-5000 second-stage implant cranioplasties/year. Unfortunately, the common tumor defect cranioplasty is reconstructed with on-table manipulation of titanium mesh, liquid polymethylmethacrylate (PMMA), liquid hydroxyapatitie/bone cement (HA) or autologous split-thickness calvarial bone grafts, which forces the surgeon to shape/mold these materials to an approximate size/shape. This results in some form of craniofacial asymmetry and a post-operative appearance which is suboptimal. Furthermore, the difficult shaping process may take several hours—which in turn increases anesthesia, total blood loss, risk for infection, morbidity, and all costs associated with longer operative times. Therefore, there is significant opportunity to extend this CAPE to thousands of patients.

In 2002, the advent of computer-aided design and manufacturing (CAD/CAM) was used for the first time to pre-emptively match the contralateral, non-operated skull for ideal contour and appearance—and thus the CCI was born. However, cranioplasties with these “perfect” implants can only be performed as “second stage” operations—to ensure that the CCI fits perfectly into the skull defect. In recent years, there have been several reports demonstrating the feasibility of CCIs for “single-stage cranioplasty”—by using a handheld bur to shave down the implant artistically. Although limited, the authors report acceptable outcomes, a trend towards decreased operative times, and less overall surgery required (i.e., one stage instead of two). The main challenges are limitations in both assessing and predicting each tumor-resection deformity pre-surgery. This thereby limits the applicability of CCIs in this patient population. Various barriers include 1) unknown exact tumor size, 2) unknown growth from time of pre-op CT scan-to-actual day of surgery, and 3) the unknown resection margins needed to minimize local recurrence. For these cases, the CCI would need to be reshaped/resized intraoperatively from a size slightly larger than expected—which is a process that may take several (2-4) hours. However, there are currently no established planning and execution systems available to assist these single-stage reconstructions. Therefore, this Computer-Assisted Planning and Execution (CAPE) system will assist surgeons in performing single-stage cranioplasty following oncological resection. This disclosure covers the entire CAPE system, which is a single, seamless platform capable of both planning (pre-op use) and navigation (intra-op use)—distinctly different than all other current systems that do either one or the other (see Table 2 below). In addition, its hardware such as trackable cutting guides and rigid cranial reference mount (described herein) are each uniquely valuable. The CAPE architecture will provide reconstructive surgeons all of the necessary algorithms for real-time updates related to single-stage customized implant cranioplasty.

TABLE 2 Comparison of CAPE and Competitive Solutions. Innovation Med Surg Praxim/ Smith & Group Brainlab Services Medtronic Paritic Ortho Surg Siemens Nephew Stryker Zimmer CAPE Virtual ✓ X ✓ X X X X X X X ✓ Planning Navigation ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ Realtime X X X X X X X X X X ✓ cephalometrics Trackable X X X X X X X X X X ✓ cutting guides Biomechanical X X X X X X X X X X ✓ Simulation Multiple X X X X X X X X X X ✓ stations

FIG. 15 illustrates a perspective view of a surgical guide assembly 1500. The surgical guide assembly 1500 may be similar to the surgical guide assemblies 203-D, 203-R shown in FIGS. 2A-2C and the surgical guide assembly 203 shown in FIGS. 7A and 7B. The surgical guide assembly 1500 may include a body 1510 and one or more arms (three are shown: 1520). The body 1510 may have one or more openings (two are shown: 1512) formed at least partially therethrough.

The arms 1520 may be coupled to or integral with the body 1510. The arms 1520 may be circumferentially-offset from one another around the body 1510 from about 5° to about 175°, about 20° to about 160°, about 45° to about 135°, or about 60° to about 120°. As shown, the arms 1520 are circumferentially-offset from one another by about 120°. The arms 1520 may each include an opening 1522 formed therethrough. In at least one embodiment, one or more of the arms 1520 may also include a swivel joint 1530 (e.g., a spherical bearing), which the opening 1522 may extend therethrough. The swivel joint 1530 may allow a central longitudinal axis through the opening 1520 to tilt in two or three dimensions, as described in more detail below. In at least one embodiment, the swivel joint 1530 may permit angular rotation about a central point in two orthogonal directions.

FIG. 16 illustrates a side, cross-sectional view of the surgical guide assembly 1500, and FIG. 17 illustrates an exploded side, cross-sectional view of the surgical guide assembly 1500. As shown, the body 1510 may at least partially overlap one of the arms 1520. This may cause a first one of the openings 1512-1 through the body 1510 to be longer than a second one of the openings 1512-2 through the body 1510. In other embodiments, the body 1510 may not at least partially overlap any of the arms 1520, or the body 1510 may at least partially overlap two or more of the arms 1520. The openings 1512 in the body 1510 may be at least partially defined by a threaded inner surface 1514 of the body 1510. As such, the openings 1512 in the body 1510 may be configured to receive rods having corresponding threads, as discussed in greater detail below.

The swivel joints 1530 in the arms 1520 may each include an outer member or ring 1532 and an inner member or ring 1534. The inner surface of the outer ring 1532 and the outer surface of the inner ring 1534 may have complimentary curved surfaces that allow the inner ring 1534 to move (e.g., swivel, pivot, and/or rotate) with respect to the outer ring 1532. For example, a central longitudinal axis 1535 through the inner ring 1534 may be configured to tilt to an angle with respect to a central longitudinal axis 1533 through the outer ring 1532. The angle may be from about 1° to about 15°, about 1° to about 30°, about 1° to about 45°, or more. In addition, the direction that the inner ring 1534 tilts with respect to the outer ring 1532 may be from about 0° to about 360° about the central longitudinal axis 1533 through the outer ring 1532 as measured in a plane that is perpendicular to the central longitudinal axis 1533 through the outer ring 1532. In other words, the swivel joints 1530 may have two degrees of freedom.

The inner ring 1534 may have an opening formed therethrough that is configured to receive a sleeve 1536. The sleeve 1536 may have the opening 1522 formed therethrough. As shown, the cross-sectional length (e.g., diameter) of the inner surface of the sleeve 1536 may vary. For example, the inner surface of the sleeve 1536 may define a shoulder 1538 (see FIG. 17) proximate to a lower side of the sleeve 1536. A screw or other fastener 1540 may be inserted into the opening 1522 in the sleeve 1536 and come to rest against the shoulder 1538. The sleeve 1536 and the inner ring 1534 maybe separate components, or they may be integral with one another. Similarly, the arm 1520 and the outer ring 1532 may be separate components, or they may be integral with one another.

The arms 1520 may be oriented at an angle 1524 with respect to the body 1510. The angle 1524 may be from about 90° (i.e., perpendicular to the body 1510), to about 170°, about 100° to about 160°, or about 110° to about 150°. As shown, the angle is about 110°. As a result, a central longitudinal axis 1516 through the opening 1512 in the body 1510 may be oriented at an angle 1518 with respect to the central longitudinal axis 1533 through the outer ring 1532. The angle 1518 may be from about 1° to about 85°, about 10° to about 70°, or about 20° to about 60°. As shown, the angle is about 20°.

FIG. 18 illustrates a perspective view of the surgical guide assembly 1500 shown in FIG. 15 with thumbscrews 1550 for securing a position of the swivel joints 1530. In at least one embodiment, each of the swivel joints 1530 may include one or more thumb screws (two are shown 1550). The thumb screws 1550 may be circumferentially-offset from one another about the central longitudinal axis 1533 through the outer ring 1532. For example, the thumb screws 1550 may be circumferentially-offset from one another from about 45° to about 135°, about 60° to about 150°, or about 75° to about 165° with respect to the central longitudinal axis 1533 through the outer ring 1532. As shown, the angle between the thumb screws 1550 is about 120°.

FIGS. 19 and 20 illustrate a side, cross-sectional view and an exploded side, cross-sectional view, respectively, of the surgical guide assembly 1500 shown in FIG. 18. The thumb screws 1550 may extend at least partially through each arm 1520 and into contact with the outer ring 1532, the inner ring 1534, or both. In at least one embodiment, the thumb screws 1550 may extend at least partially through the arm 1520 and the outer ring 1532 and into contact with the outer surface of the inner ring 1534. When tightened, the thumb screws 1550 may secure the inner ring 1534 in a fixed position with respect to the outer ring 1532 such that the central longitudinal axis 1535 through the inner ring 1534 is at the desired angle with respect to the central longitudinal axis 1533 through the outer ring 1532. Although shown as thumb screws 1550 that may be rotated by hand, in other embodiments, other mechanical devices or fasteners may be used to secure the inner ring 1534 in a fixed position with respect to the outer ring 1532.

FIG. 21 illustrates a perspective view of the surgical guide assembly 1500 coupled to a skull 2100. The surgical guide assembly 1500 may be placed against a bone (e.g., skull) 2100 to which it is to be coupled. Although not shown, in another embodiment, the surgical guide assembly 1500 may be placed against the soft tissue (e.g., skin) covering the bone to which it is to be coupled. The person holding the surgical guide assembly 1500 may move or adjust the position of the surgical guide assembly 1500 until the lower surfaces 1537 of the sleeves 1536 are substantially flat against the skull 2100. More particularly, moving the surgical guide assembly 1500 may cause the inner ring 1534 to move or pivot with respect to the outer ring 1532 until the lower surfaces 1537 of the sleeves 1536 are substantially flat against the skull 2100. When the thumb screws 1550 are present (as shown in FIGS. 18-20, they may then be tightened to maintain the lower surfaces 1537 of the sleeves 1536 substantially flat against the skull 2100.

The screws 1540 may be inserted into the swivel joints 1530. More particularly, a screw 1540 may be inserted into the opening 1522 in the sleeve 1536 of each swivel joint 1530. The screws 1540 may be rotated causing them to bore at least partially into the skull 2100. This may couple the surgical guide assembly 1500 to the skull 2100. Although shown coupled to a human skull 2100, in other embodiments, the surgical guide assembly 1500 may be coupled to another human bone or to the bone of another species.

Either before or after the surgical guide assembly 1500 is coupled to the skull 2100, one or more rods (two are shown: 1560) may be inserted into the openings 1512 in the body 1510. The rods 1560 may include threaded outer surfaces that may form a threaded connection with the threaded inner surfaces 1514 defining the openings 1512. Once inserted and connected, the rods 1560 may extend outward from the body 1510 and/or the skull 2100. One or more trackable features (one is shown: 1570) may be coupled to distal ends of the rods 1560. The trackable feature 1570 may be optical trackable features. For example, the trackable feature 1570 may be made of a reflective material (e.g., a reflective sphere). In other embodiments, the trackable feature 1570 may not be optical trackable feature. The trackable feature 1570 may be similar to the fragment reference modules 201-D and 201-R shown in FIG. 2B.

The terms “couple,” “coupled,” “connect,” “connection,” “connected,” “in connection with,” and “connecting” refer to “in direct connection with” or “in connection with via one or more intermediate elements or members.” Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” As used herein, the phrase “one or more of”, for example, A, B, and C means any of the following: either A, B, or C alone; or combinations of two, such as A and B, B and C, and A and C; or combinations of three A, B and C.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. 

What is claimed is:
 1. A surgical guide assembly, comprising: a body having an opening formed at least partially therethrough; an arm extending from the body; a joint positioned at least partially in the arm, wherein the joint comprises: an outer ring; and an inner ring, wherein the inner ring is configured to move with respect to the outer ring such that an angle between a central longitudinal axis through the inner ring varies with respect to a central longitudinal axis through the outer ring.
 2. The surgical guide assembly of claim 1, wherein the joint is a spherical bearing.
 3. The surgical guide assembly of claim 1, further comprising a sleeve positioned at least partially in the inner ring, wherein the sleeve is configured to move with respect to the outer ring, and wherein an opening is formed through the sleeve.
 4. The surgical guide assembly of claim 3, wherein an inner surface of the sleeve that defines the opening includes a shoulder.
 5. The surgical guide assembly of claim 4, further comprising a screw that is positioned at least partially in the opening in the sleeve and configured to contact the shoulder.
 6. The surgical guide assembly of claim 1, further comprising: a rod at least partially positioned in the opening in the body; and a trackable feature coupled to the rod.
 7. The surgical guide assembly of claim 6, wherein the trackable feature comprises an optical trackable feature.
 8. The surgical guide assembly of claim 1, further comprising a screw extending at least partially through the arm and in contact with the outer ring, the inner ring, or both.
 9. The surgical guide assembly of claim 8, wherein the screw extends at least partially through the outer ring and contacts an outer surface of the inner ring, and wherein the screw secures the inner ring in a fixed position with respect to the outer ring when the screw contacts the inner ring.
 10. The surgical guide assembly of claim 1, wherein the central longitudinal axis through the outer ring is oriented at an angle from about 1 degree to about 85 degrees with respect to a central longitudinal axis through the opening in the body.
 11. A surgical guide assembly, comprising: a body having an opening formed at least partially therethrough; a rod at least partially positioned in the opening in the body; a trackable feature coupled to the rod; an arm extending from the body; a joint positioned at least partially in the arm, wherein the joint comprises: an outer ring; an inner ring, wherein the inner ring is configured to move with respect to the outer ring such that an angle between a central longitudinal axis through the inner ring varies with respect to a central longitudinal axis through the outer ring, and wherein the central longitudinal axis through the outer ring is oriented at an angle from about 1 degree to about 85 degrees with respect to a central longitudinal axis through the opening in the body; and a sleeve positioned at least partially in the inner ring, wherein the sleeve is configured to move with respect to the outer ring, and wherein an opening is formed through the sleeve.
 12. The surgical guide assembly of claim 11, wherein an inner surface of the sleeve that defines the opening includes a shoulder, and further comprising a screw that is positioned at least partially in the opening in the sleeve and configured to contact the shoulder.
 13. The surgical guide assembly of claim 11, further comprising a screw extending at least partially through the arm and in contact with the outer ring, the inner ring, or both.
 14. The surgical guide assembly of claim 13, wherein the screw extends at least partially through the outer ring and contacts an outer surface of the inner ring, and wherein the screw secures the inner ring in a fixed position with respect to the outer ring when the screw contacts the inner ring.
 15. The surgical guide assembly of claim 11, wherein the arm comprises a plurality of arms that are circumferentially-offset from one another around the body.
 16. A method for attaching a surgical guide assembly to a bone, comprising: placing the surgical guide assembly against the bone or soft tissue covering the bone, wherein the surgical guide assembly comprises: a body having an opening formed at least partially therethrough; an arm extending from the body; a joint positioned at least partially in the arm, wherein the joint comprises: an outer ring; and an inner ring, wherein the inner ring is configured to move with respect to the outer ring such that an angle between a central longitudinal axis through the inner ring varies with respect to a central longitudinal axis through the outer ring; and inserting a first screw into an opening in the inner ring and at least partially into the bone, wherein the first screw couples the surgical guide assembly to the bone.
 17. The method of claim 16, wherein the joint further comprises a sleeve positioned at least partially in the inner ring, wherein the sleeve is configured to move with respect to the outer ring, and wherein the opening in the inner ring extends through the sleeve.
 18. The method of claim 17, further comprising adjusting a position of the surgical guide assembly until a surface of the sleeve that contacts the bone of the soft tissue covering the bone is substantially flat against the bone.
 19. The method of claim 16, further comprising tightening a second screw that extends at least partially through the arm and in contact with the outer ring, the inner ring, or both.
 20. The method of claim 16, further comprising inserting a rod at least partially into the opening in the body, wherein the rod has a trackable feature coupled thereto. 